Vol. 17, No. 6 A N A LY T IC A L EDITION
INDUSTRIAL
AND
ENGINEERING CHEMISTRY
S C I E N C E I S P O W E R
ARKS OF DRUG MANUFACTURERS
a r e s a f e g u a r d e d i n t h e l a b o r a t o r y !
D ru g s a n d p h a rm a c e u tic a ls —th e P h y sic ia n s’ g re a t allies. T h e y p ro te c t fam ilies. T h e y reliev e p ain . T h ey re s to re h e a lth .
M a n u fa c tu re rs o f d ru g s a n d p h a rm a c e u tic a ls k n o w th e p a ra m o u n t im p o rta n c e o f q u a lity . T h e y cease
lessly te st to in s u re in g re d ie n t q u a lity a n d fo rm u la u n ifo rm ity . Every step in m a n u f a c tu r in g m u s t be c a re fu lly sa fe g u a rd e d . Lives m u s t be p ro te c te d . R e p u ta tio n o f p re c io u s tra d e m a rk s m u s t be m a in ta in e d . In th e la b o r a to r ie s (p r o d u c t c o n tro l ro o m s) o f m a n y o f th e le a d in g d ru g a n d p h a rm a c e u tic a l co m p an ies o f A m erica y o u w ill find a to o l o f m eas
u re m e n t th a t g u a rd s p re c io u s tra d e m a rk s.
I t is B a k e r’s A n aly zed C .P . C h em icals an d A cids. T h e re a so n th ese R e a g e n ts have been selected is r a th e r u n iq u e fo r B a k e r’s A n aly zed
C .P. C h em icals b e a r th is d is tin c tio n . E ach b o ttle h as th e a ctu a l lo t analysis on th e label. T h e sm all p erc e n ta g e s o f im p u ritie s, as fo u n d by B a k e r’s a n aly sts a n d by lo t analysis, are p rin te d o n th e lab el.
C h em ists w h o w o rk in te rm s o f th ir d a n d fo u r th d ecim al ex actn ess k n o w th e v a lu e o f th e a c tu a l an aly sis ra th e r th a n a la b e l th a t sim p ly b ears th e s ta te m e n t o f m a x im u m lim its o f im p u ritie s.
So o n y o u r n e x t o rd e r, be su re to specify B a k e r’s A n a l y z e d C . P . C h e m i c a l s a n d A c i d s . Y o u r fa v o rite la b o r a to r y su p p ly h o u se c a n su p p ly you.
J. T. B a k e r C h e m ica l Co., Exe cu tive O ffice s a n d Plant:
P h illip sb u rg , N e w Jersey. B ra n ch O ffice s: N e w Y o rk , P h ila d e lp h ia a n d C h ica go .
Purity defined — not to " m a x i, m um lim it»"— but to tfw deci
m a l b y a c t u a l t a t a n a l y s U . That'» the »tary o f the Balter'»
P I T T S B U R G H
m - t * b u r c 'itiä V k ;ic *tu
M O N T R E A L C A N A D A
Laboratories have at their command in these four conveniently-located d istrib u tio n p la n ts, la rg e and com prehensive stocks o f both laboratory apparatus and reagent chemicals.
D evelopm ent Laboratories, Chemical M anufactur
ing Laboratories, Instrument Shops, Glass Shops and Service Departments are maintained to help meet the laboratory’s requirements for up-to-date equipment.
F i s h e r S c i e n t i f i c C o . E i m e r
a n dA m e n d
7 17 F o rb e s S tr e e t P it ts b u r g h , P a. 6 3 5 G r e e n w ic h S tre e t N e w Y o r k , N . Y .
F i s h e r S c i e n t i f i c Co. Fisher Scientific Co.,
l t d.
2 1 0 9 L o c u s t S tr e e t S t. L o u is, M is s o u ri 9 0 4 S t. Ja m e s S tr e e t M o n tr e a l, P . Q .
IN D U S T R I A L a n d E N G I N E E R IN G C H E M IS T R Y
A N A L Y T I C A L E D I T I O N
W A L T E R J. M U R P H Y , E D I T O R I S S U E D J U N E 18, 1945 V O L . 17, N O . 6 C O N S E C U T I V E N O . 12
M anuscript Editor: G . Gl a d y s Go r d o n
R . P. Ch a p m a n
J. R. Ch u r c h i l l
B. L. Cl a r k e
Lawrence T. Hallett, Associate Editor M anuscript Assistant: St e l l a An d e r s o n
Advisory Board T . R . Cu n n i n g h a m
G. E. F. Lu n d e l l M . G. Me l l o n
M ake-up Assistant: Ch a r l o t t e C. Sa y r e
R. H. Mü l l e r
B. L . Os e r
H . H . Wi l l a r d
S p ectrograp h ic A n a ly sis o f M a g n e siu m A lloys . . . B. L. A verbach 341 N e o p e n ta n e in R efinery B u t a n e s ...
L. C. Jones, Jr., R. A. Friedel, an d G . P. Hinds, Jr. 349 D e te r m in a tio n o f A lu m in u m C hloride a n d H yd ro
c h lo ric A cid in H ydrocarbon S t r e a m s ...
W alter G reen an d S. R. Baker 351 D e te r m in a tio n o f T etra eth y llea d in G a so lin e . . .
Louis Lykken, R. S. Treseder, F. D. Tuemmler, and Victor Zahn 353 D e te r m in in g A ro m a tic C o n te n t o f C racked G a so
lin e s by S p ecific D isp ersio n . . Sigurd G roennings 361 D e te r m in a tio n o f U n sa tu r a tio n in B u ty l R ubber
John Rehner, Jr., an d Priscilla G ray 367 F lu o ro m etrio D e te r m in a tio n o f R iboflavin in Eggs
W alter J. Peterson, R. S. Dearstyne, R. E. Comstock, and V irginia W eldon 370 P h o to m e tr ic D e te r m in a tio n o f F lu o silic ic A cid in
H ydrofluoric A c i d ...G eorge N. C ade 372 D e te r m in a tio n o f V ita m in C in P resen ce o f I n te r
ferin g R ed u cin g S u b s t a n c e s ...
A ubrey P. Stewart, Jr., and Paul F. Sharp 373 E lectr o ly tic D e te r m in a tio n o f C opper an d Z in c in
Brass P la tin g B a th s a n d in B rass E lectr o d e p o sits A. S. Miceli an d R. E. Mosher 377 S ta n d a rd s in V ita m in A A s s a y s ...
Elizabeth Crofts Callison a n d Elsa O rent-Keiles 378 C olorim etric D e te r m in a tio n o f N ick el w ith D i-
m e th y lg ly o x im e . A. M. Mitchell with M. G . Mellon 380
D e te r m in a tio n of M o istu re in N aval S to res P rod u cts b y K arl F isch er M e t h o d ...
Victor E. G rotlisch an d H arold N. Burstein 382 E s tim a tio n o f R iboflavin, T h ia m in e , an d A P-M ethyl-
n ic o tin a m id e . . . . Robert E. Johnson, Frederick Sargent, Paul F. Robinson, an d Frank C. Consolazio 384 V a cu u m D ryin g A p p aratu s for U n sta b le P o ly m er ic
M a t e r i a l s ... A. R. Kemp and W. G . Straitiff 387 In s tr u m e n t for M ea su rin g T h ic k n e ss o f N o n c o n
d u c tin g F ilm s A pplied over N o n m a g n e tic M eta ls Allen L. A lexander, Peter King, an d J. E. D inger 389 D e te r m in a tio n o f Iod in e in T h yroid by C erate O xi
d im e tr y ...
D. T. Englis and A ugusta A. K noepfelm acher 393 M ICROCHEM ISTRY
D e te r m in in g th e H ydroxyl C o n te n t o f C ertain O rganic C o m p o u n d s ...
C. L. O gg, W. L. Porter, and C. O. Willits 394 S e m im ic r o -K je ld a h l N itro g en D e te r m in a tio n . .
Irving Allan Kaye an d Nathan W einer 397 M ic r o d e te r m in a tio n o f C opper w ith P olarograph
Christopher C arruthers 398 S p e c tro p h o to m etric M eth o d for D e te r m in in g
F o r m a ld e h y d e ...
Clark E. Bricker an d H ilding R. Johnson 400 BOOK R E V I E W ... 402 NOTES ON ANALYTICAL PROCEDURES
C a ta ly tic A c tiv ity o f S e le n a te s in th e K jeld a h l M eth o d for D e te r m in a tio n o f N itro g en . . . .
Robert S. Dalrymple an d G . Brooks King 403 A u to m a tic G as C ircu la tin g P u m p ...
J. H. Simons, T. J. Brice, and W. H. Pearlson 404
T h e A m erica n C h em ica l S o c ie ty assu m es n o r e sp o n sib ility for th e sta te m e n ts an d o p in io n s a d v a n c ed b y co n trib u to rs to it s p u b lica tio n s.
3 2 ,0 0 0 co p ies of th is is s u e p rin ted . C o p y r ig h t 1945 b y A m erican C h e m ica l S o c ie ty ,
P u b lish ed b y th e A m erican C h em ica l S o c ie ty a t E a s to n , P a . E d i
to ria l Office: 1155 16th S tre et, N . W ., W a sh in g to n 6 , D . C . ; telep h o n e, R ep u b lic 5301; ca b le, J ie ch em (W a sh in g to n ). N e w Y ork E d ito ria l B ran ch : 60 E a s t 4 2n d S treet, N e w Y ork 17, N . Y .; telep h o n e, M u rray H ill 2 -4 6 6 2 . C h ica g o E d ito ria l B ra n ch : 3 1 0 S o u th M ich ig a n A v en u e , C h ica g o 4, 111.;
te lep h o n e, W a b a sh 7 3 76. B u sin ess Office: A m erica n C h e m ic a l S o cie ty , 1155 16th S tree t, N . W ., W a sh in g to n 6 , D . C . A d v e r tisin g Office: 3 3 2 W e st 4 2n d S tr eet, N e w Y o rk 18, N , Y .; telep h o n e, B r y a n t 9-4430.
E n tere d as seco n d -cla ss m a tte r a t th e P o s t Office a t E a s to n , P a ., u nd er th e A c t o f M a rch 3 , 1 8 79, as 2 4 tim e s a y ea r— I n d u stria l E d itio n m o n th ly on th e 1st, A n a ly tic a l E d itio n m o n th ly on th e 15th . A ccep ta n ce fo r m a ilin g a t s p e c ia l r a te o f p o sta g e p ro v id ed for in S ectio n 1103, A c t of O cto b er 3 , 1917, a u th o r ized J u ly 13, 1918.
R e m itta n c e s an d orders for su b scrip tio n s an d for sin g le co p ies, n o tice s of ch a n g es of ad d ress a n d n ew p ro fessio n a l co n n ectio n s, an d cla im s for m issin g n um b ers sh o u ld b e s e n t to th e A m erica n C h e m ica l S o c ie ty , 1155 16th S treet, N . W ., W a sh in g to n 6, D . C . C h a n g es of ad dress for th e In d u stria l E d itio n
m u st b e re ceiv e d on or b efo re th e 18th of th e p reced in g m o n th a n d fo r th e A n a ly tic a l E d itio n n o t la te r th a n th e 3 0 th of th e p reced in g m o n th . C laim s for m issin g n um b ers w ill n o t b e a llo w ed (1) if receiv ed m ore th a n 60 d a y s from d a te of issu e (o w in g to th e h azard s of w a rtim e d e liv e ry , no claim s can be h o nored fro m sub scribers o u tsid e of N o rth A m eric a ), (2) if lo ss w as d u e to fa ilu re of n o tic e of ch a n g e of ad dress to b e receiv ed before th e d a te s specified in th e p rec ed in g s e n ten c e, or (3) if th e reason for cla im is “ m issin g from files’’.
A n n u a l su b scrip tio n — In d u str ia l E d itio n a n d A n a ly tic a l E d itio n sold o n ly as a u n it, m em b ers $3 .0 0 , n o nm em bers $4 .0 0 . P o sta g e to co u n tries n o t in th e P a n -A m eric a n U n io n $2.25; C anad ian p o sta g e $0.75. S in g le cop ies—
cu rren t issu es, In d u stria l E d itio n $0 .7 5 , A n a ly tic a l E d itio n $0.50; back n um b ers In d u stria l E d itio n $0 .8 0 , A n a ly tie a l E d itio n p rices on r e q u e s t;
sp e c ia l rates to m em bers.
T h e A m erican C h em ical S o c ie ty also p u b lish es C h em ic a l a n d E n g in e e r in g N e w s , C h em ica l A b stra cts , an d J o u r n a l o f the A m e r ic a n C h em ic a l S ociety.
R a tes on requ est.
I N D U S
Top — This is one of the Gas Analysis Cabi
nets which has made history among sulfur- burner users, by its speed, its accuracy and the small amount of attention it requires.
The Micromax instrument to which it reports is shown a t right.
R ight— Whether it is used as a Recorder or automatic Controller depends on the user’s wishes; this Micromax is outstandingly responsive and dependable for either service.
HERE ARE RESULTS
From M a n y Users of Micromax SO2 Control
All around the country— in oil refineries, paper mills, steel mills and chemical p lan ts— are sulfur burners which regularly deliver their product— S0 2—-at a concentration which is within one per cent of the desired strength. This means th a t production is helped—sulfur is saved
— time of busy men is conserved.
T h at, in general, is the condition we have found by a survey among several dozen plants. B ut we’ve found out m ore— we’ve found how this uniform ity is m aintained. And it adds up to a strong endorsem ent of Micromax S 02 Recorders and Controllers.
For, every single M icromax oper
ator who replied said th a t he is hold
ing S 0 2 to within th at one per cent!
Jrl. A d N -91 (4a)
Idepends on m e!
A S lo g a n F or E t e r y A m e r ic a n
Furtherm ore, seventy out of every hundred M icromax users said they find “ no variation” from the desired strength! In contrast, only 39 per cent of the non-M icromax users could claim perfect control, and 35 per cent were getting results worse than any M icromax user reported.
M icromax S 02 instrum ents have five features which help explain the superiority of their results:
1. T h e t h e r m a l- c o n d u c t i v i ty m ethod of analysis is used— it’s fast, sensitive, all-electric.
Gas is sampled practically a t the burner, and control is ap
plied with speed and precision.
All S 0 2 passages are corrosion- proof. The only filter is a coke
P-
? > llj 15 9 2.
3.
tower, which requires renewing only a t long intervals. Even if the aspirator pulls some acid m ist into the analysis cell, the operator merely cleans it and re-connects it to the filter.
4. M aintenance is no problem ; the equipm ent needs no more a t
tention than does a base-metal pyrom eter.
5. The Micromax R ecorder— pre
cise, sensitive, fully autom atic and entirely dependable for re
cording, controlling or both.
An L&N engineer will either call to discuss an S 02 control problem, or will send Folder N -9 1 (l), as you prefer.
L E E D S & N O R T H R U P C O M P A N Y , 4920 S T E N T O N A V E ., P H I L A . 44, P A .
L E E D S & N O R T H R U P
M E A S U R I N G I N S T R U M E N T S T E L E M E T E R S A U T O M A T I C C O N T R O L S H E A T - T R E A T I N G F U R N A C E S
T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 17, No. 6
June, 1945 A N A L Y T I C A L E D I T I O N 5
Pump and a Pressovac Pump into a compact, econom ical vacuum source.
It w ill attain better than 0.01 micron at a sp eed in ex cess of 3 liters per second without the use of a cold trap. The vapor pressure of Amoil used as the pumping medium is so low that the amount of oil vapor diffusing out of the pump is n eg li
gible. The "Pyrex” brand glass diffusion pump is of the semi-fractionating type although of single-stage construction. The forepressure is provided by a motor- driven C enco Pressovac. The heater current required is .8 to 1.2 amperes.
No. 93270A Vacuum Pump Outfit, C enco O il Diffusion Type, for operation on 115 volts, 60 cy cles A.C. is supplied with a sufficient quantity of Amoil at $100.
"C enco N e w s C h a ts ," c o n ta in in g in fo rm a tio n on n e w la b o r a to r y ite m s , are a v a ila b le upon r e q u e s t to te c h n ic a l p e r s o n n e l in e d u c a tio n a l a n d in d u s tr ia l in s titu tio n s.
CENTRAL SCIENTIFIC COMPANY
S C I E N T I F I C I N S T R U M E N T S ( T N iT ) L A B O R A T O R Y A P P A R A T U S
iMrV'oCfr.
NEW YORK TORONTO C H I C A G O BOSTON SAN FRANCISCO
6 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 17, No. 6
a Letter to
an Advertising Agency*
P o r o c e l
* T h is letter w a s w ritten b y a n en gin e e r«»n o t a n a d v e rtisin g m an. It w a s in te nde d s im p ly to s u p p ly in fo rm atio n fo r a P orocel a dvertise m e nt o n this p a g e this m onth. But the letter w a s s o d e a r a n d c o n c ise a n outline of P oro- c e l's properties that the co p yw rite r said/to h im self, “ W h y gild the lily ? W h y not just run this letter a s written a n d re c e iv e d ?” . . . s o here it is.
June, 1945 A N A L Y T I C A L E D I T I O N 7
v t e r * :
« r< e* e t
a f d i ^
!
a n A o « vC b i e ®^0
P U Y P O N D S
8 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 17, No, 6
I N F R A R E D T R A N S M I S S I O N
as recorded with this
I N F R A R E D S P E C T R O M E T E R
T h e P e rk in -E lm e r In fra re d S p ectro m eter M odel 12B an d its accessories a re designed to m ak e th e an aly sis o f com plicated m ix tu res o f organic com p o u n d s as d ire c t a n d sim ple as possible. M o st o f th e u su al b o ttlen eck s in in frared sp e c tro p h o to m e try , such as th e calcu latio n o f p e rc e n t tra n s m ission cu rv es for s ta n d a rd com pounds, loss an d change o f com position o f sam ples b y ev a p o ra tio n , an d g alv a n o m e te r in s ta b ility p roblem s are e lim in ated b y p ro p e rly designing th e e q u ip m e n t to o p e ra te on so und p h y s
ical principles. T h e in s tru m e n t records d ire c tly th e ap p ro x im ate p ercen t tran sm issio n o r o p tical d e n sity cu rv e o f a n y sam ple, m ak in g i t easy to o b ta in sta n d a rd tran sm issio n cu rv es fo r th e p u re co m pounds in a m ixture.
T h e selection o f th e o p tim u m w av elen g th s for d eterm in in g each co m p o n en t o f a new m ix tu re can be m ade d ire c tly from th e p u re com pound tra n s m ission curves. P recise ex tin ctio n coefficients for use as sta n d a rd s in q u a n tita tiv e analysis are o b ta in e d from th e cu rv es by app ly in g to th em sm all repro d u cib le co rrections (plus o r m inus a few p e rc e n t). B esides m aking it easy to se t u p new analyses, th e im p ro v ed e q u ip m e n t gives m ore accu rate resu lts a fte r th e a n a ly tic a l p ro ced u re is se t u p. T h e use o f th e electronic am plifier* elim inates th e c u sto m a ry d rift a n d v ib ra tio n problem s o f a h ig h -sen sitiv ity g alv an o m eter. T ig h tly -sealed a b so rp tio n cells w ith good sam p le h an d lin g e q u ip m e n t m ak e i t easy to m easu re th e sp e c tra o f low- boiling liquids. T h e ir sm all volum e p e rm its th e m easu rem en t o f a com plete s p ectru m w ith on ly a few te n th s o f a cc. o f sam ple. F o r gas sam ples, re
m o v ab le ab so rp tio n cells are now av ailab le w ith p a th le n g th s u p to a m eter, m ak in g possible d e te c tio n o f otherw ise im p ercep tib le tra c e com ponents.
T h e sp e c tru m o f liq u id benzene show n above illu s tra te s th e perform ance o f th e P e rk in -E lm e r In fra re d S p ectro m eter M odel 12B in recording d ire c tly th e p e rc e n t transm ission o f a sam ple 0.045 m m - th ick . T h e sp ectru m is an u n reto u ch ed rep ro d u ctio n o f th e original record in th e ran g e from 7.5 to 14.5 m icrons m a d e w ith an o p a q u e sh u tte r.
* T h is am plifier is obtainable only by those working directly or indirectly f o r the Government.
S P E C I A L F E A T U R E S Direct recording of percent trans
mission curves.
Equipped for gas, liquid, and solid samples.
Removable absorption cells up to
100 cm. path.
Tightly-sealed liquid cells.
Convenient cabinet mounting of all parts.
High resolution over long spectral range with simply changed prisms.
Individual temperature correction of wavelength scale for each prism.
Optional horizontal absorption cell slide for quick change of cells.
Optical speed f:4.5; 60° prism face 60 x 75 mm.; off-axis parabolic colli- mation.
Compact (12"x31"x9"), sturdy de
sign; airtight covers to permit reduc
tion of atmospheric interferences.
Selective shutters to reduce scattered light.
Multi-speed wavelength drive.
TH£ P £R K in -< Lm !l\ CORPORATION!
G L c n B R O c m - c o n n -
lune, 1945 A N A L Y T I C A L E D I T I O N 9
MERCK has
THE RIGHT COMBINATION
for Laboratory Chemicals
One o f th e unique “ M erck Cross T ables’’ in th e M erck A nalytical Laboratories.
D eterm ination o f com parative m elting points in th e M erck R esearch Laboratories.
F ine chemicals for th e professions and industry since 1818.
A corner o f the M erck Packaging Laboratory.
I— MERCK & CO., Inc.
Please send m e th e following ch arts:
□ S ensitivity of Q u alitativ e R eactions
□ Periodic C h a rt of th e E lem ents
□ S en sitiv ity C h a rt
N a m e ...
C o m p an y ... P o sition.
S tre e t ...
RAHWAY, N .J.— i
I N D . E N G . C H E M - 6-15-45
... I
C it y ... S t a t e .
L . J
10 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 17, No. 6
In the m anufacture of Pyrex, Vycor and C orning brand Laboratory G lassw are som e operation s are autom atic, but skilled hands are usually req uired som ew here along the line. Special apparatus, for example, is alm ost com pletely hand fabricated.
In C orning Lamp Shops, com plicated apparatus is expertly fabricated by crafts
m en of lo n g experience. O ne out o f every three o f these highly skilled artisans has gone to war. T h eir sensitive fingers that once m anipulated glass in the flame o f a blow to rch now squeeze a trigger. It takes years to m ake a Lamp W o rk er—to replace them is alm ost im possible.
T hose w ho rem ain are do in g th eir utm ost to supply the A rm ed Forces w ith all the Pyrex, V ycor and C orning brand Laboratory G lassw are they need.
T hese are the reasons—and we are sure you w ill understand—why special appa
ratus is difficult to obtain and why your laboratory supply dealer may som etim es be unable to furnish even our standard catalog items prom ptly.
W hen V ictory comes, then skilled C orning craftsm en w ill return. T hen there w ill be am ple stocks at your d ealer’s. A nd then you can obtain the special apparatus you need from C orning Lamp Shops.
PYREX,
“P yrex,” “ Vycor” a n d “Corning” are registered trade-m arks a n d indicate m anufacture by
C O R N I N G G L A S S W O R K S • C O R N I N G , N. Y.
P y R t X
B A L A N C E D F O R A L L - A R O U N D U S E
brand LABORATORY
C orning
—m eans ---
Research in Glass
June, 1945 A N A L Y T I C A L E D I T I O N 11
*
I N S T A L L A T I O N
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S P E C I A L S E R V I C E S
It Takes AM This
TO MAKE A COMPLETE ANALYTICAL PROCESS
T
H E M A S S S P E C T R O M E T E R m ethod of a n a ly sis w a s develo ped in C on solid ate d En gin e e rin g C o m p a n y 's lab o ra to rie s over a period of five years. By su p plem en tin g the finest equipm ent w ith efficient o p e ratin g techniques an d a d v a n c e d m ethods o f d a ta reduction, the ultim ate am ou n t of u sa b le results are obtained.*
INSTRUMENT
— Each Consolidated M ass Spectrometer is supplied complete in every operating detail.
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IN STALLA TIO N -
E a c h instrum ent c o m p le te ly in sta lle d a n d o p e r a t in g in e v e ry d e ta il b e fo re re le a se to p u rc h a s e r. The value of this policy of installing the mass spectrometer and training technicians in its operation
and maintenance is demonstrated by the fact that in most installations the in
strument has been placed in routine operation immediately after installation.
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I N S T R U C T I O N
— Complete instruction during installation on:(a) Instrum ent theory an d operation.
(b) Instrum ent m aintenance an d service.
(c) A n a ly s is theory a n d practice.
SPECIAL SERVICES
— Engineers are available for consultation on unusual service or operating problems. Consolidated's interest in the user and his problems includes continued development of both the instrument and its application to all analysis problems. Write Depart
ment 6-B for detailed information on how this analytical tool can help with your control, research and development problems.
A v e r a g e d e l i v e r y t i m e is 4
o r d e r , a n d i n s t a l l a t i o n a n d
C O N S O L I D A T E D E N G I N E E R I N G C O R P .
t r a i n in g a re u s u a ll y c o m p le t e d
in less th a n 6 mon ths . 5 9 5 E A S T C O L O R A D O S T R E E T • P A S A D E N A , C A L I F O R N I A
12 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y J L
Vol. 17, No. 6
F A M I L Y
O F L A B O R A T O R Y F U R N A C E S
Here a re furnaces, the like o f which la b o ra to ry technicians h a v e never seen— va stly im proved in both function an d a p p e a ra n c e . Engineered and built b y the le a d e rs in d e ve lo p in g an d m anu
facturing industrial h eat-treatin g equipment, they are the last w ord in efficient an d practical la b o ra to ry furnaces.
The Lindberg Box Furnace d e sig n e d fo r fast a n d accurate m etallurgical tests an d chemical a n a ly se s heats up to 2 0 0 0 ° F. H a s built-in trans
form er; "S te p le s s ” Input Controller an d Indicating Pyrom eter a re contained in a se p a ra te metal case.
The Lindberg Pot-Crucible Furnace d oe s salt o r le a d bath immersion tem pering, harden in g a n d an nealin g, cy a n id in g an d aluminum heat- treating. O n the other hand, a s a crucible fur
nace, it is used fo r determ ining critical points o f steel, melting b a se metals, thermocouple c a li
brations an d other necessary la b o ra to ry o p e r a tions fo r heats up to 2 0 0 0 ° F.
The Lindberg Com bustion Tube Furnace is d e sign e d fo r fa st carb on an d sulphur determ ina
tions using the volumetric method o f an alysis an d fo r gravim etric ty p e an a ly se s for carb on d e terminations o f all a llo y steels including stainless a n d heat-resisting steels. H e a ts up to 2 5 0 0 ° F.
The Lindberg Hot Plates are for precise, con
trolled all-round la b o ra to ry use for te m p e ra tures up to 9 5 0 ° F. Built-in input control provides e xa ct tem perature selection.
These furnaces can be secured from your la b o ra to ry equipm ent dealer. S e e him to d a y fo r full information.
L I N D B E R G E N G I N E E R I N G C O M P A N Y
2 4 5 0 W E ST H U B B A R D S T R E E T • C H I C A G O 12, IL L IN O IS
L in d berg
WE L L K N O W N T H R O U G H O U T T HE W O R L D A S
\
L E A D E R S I N D E V E L O P I N G A N D M A N U F A C T U R I N GI N D U S T R I A L H E A T T R E A T I N G E Q U I P M E N T
" T o
—
LD E X C L U S I V E L Y T H R O U G H L A B O R A T O R Y E Q U I P M E N T D E A L E R S
June, 1945 A N A L Y T I C A L E D I T I O N 13
T H IS IS A P A R T O F T H E S P E C T R U M O F AN ALLO Y. B Y M E A S U R IN G T H IS S P E C T R U M , P R E C IS E Q U AN TITATIVE A N A L Y S IS O F T H E C O N S T IT U E N T S IN T H E M E T A L W A S M A D E IN 15 M IN U T E S F R O M T H E T IM E TH E
S A M P L E W A S BR O U G H T INTO T H E LA B O R A T O R Y .
Accurate qualitative and quantitative analysis is being made on the A.R.L.-D 1ETERT C O M P A R A TO R -D E N SITO M - E TER after the spectrum o f the sample has been photo
graphed by an A .R.L.-D IETE R T SPEC TRO G RAPH at the City Pattern Foundry and M achine Company o f D etroit.
S PEC T R O G R A PH IC ANALYSIS is not only fast but is also econom ical.
T h e total cost is 15 cents p e r sam ple for an average volum e of w o rk . T h is m eans that silicon, m anganese, chrom ium , nickel, m olybdenum and o th er alloying m etallic constituents o r im purities may be analyzed at a cost of 3 cents o r less p er quantitative determ ination.
T w o op erato rs can analyze 10 0 to 150 sam ples per 8-hour day. O r, to put it in ano ther way, one operator alone can now do the same w o rk previously req u irin g 12 operators using older, conventional m ethods of analysis. Seventy-two elem ents can be speedily id en ti
fied on the C om parator-D ensitom eter. W ith the Spec
tro g ra p h a rap id analytical c o n tro l o f raw m aterials,
and m aterials in process is obtained. In add itio n, id e n tification o r so rtin g applications and many m iscellane
ous o r research applications beyond the scope o f ro u tin e analysis are possible.
W hen the "flat surface” sam pling technique is em ployed the analysis is virtually non-destructive to castings and finished parts. W ith th e use o f stan dard sam ples w hich are available, accuracy is largely a function of re p ro ducibility.
U se A.R.L.-DIETERT m atched spectrom etric eq u ip m ent fo r maxim um accuracy and speed.
U se the A.R.L.-DIETERT staff o f spectro g rap h ers to help you solve your analytical problem s and service your sp ectrog rap hic equipm ent.
A . R . L . - DIETERT
A P P L I E D R E S E A R C H L A B O R A T O R I E S 4 3 3 6 S A N F E R N A N D O R D „ G L E N D A L E 4 , C A L IF .
... .
- -__
H A R R Y W . D I E T E R T C O . 9 3 3 0 R O S E L A W N A V E., D E T R O IT 4 , M IC H .
HUT
14 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 17, No. 6
M U f U t f O R H A C B S
The F D -20 4 furnace below operates w ithout a transformer. The Chrom el unit is a coil of w ire w rapp ed a ro und a gro o ve d muffle. E a sy to renew, a nd durable. Top temperature about 1800° F. The heating cham ber is
7
^/2
" w id e x 5 V i" h igh x 1 4 " long.HOSKINS PRODUCTS
E L E C T R IC H E A T T R E A T I N G F U R N A C E S • • H E A T I N G E L E M E N T A L L O Y S • • T H E R M O C O U P L E A N D L E A D W IR E • • P Y R O M E T E R S • • W E L D IN G W IR E • • H E A T R E S IS T A N T C A S T IN G S • » E N A M E L IN G F IX T U R E S • • S P A R K P L U G E L E C T R O D E W IR E • • S P E C IA L A L L O Y S O F N IC K E L • • P R O T E C T IO N TU BE S
This is a double-bore high temperature C o m bustion Furnace. It is equipped w ith A llo y N o. 10 units a nd can be run at 2 300° F con
tin u o u sly or 2 4 0 0 ° F intermittently. Controlled b y a regulating transformer.
H o skin s Laboratory Furnaces h a v e for m a n y years foun d g o o d acceptance because of the g o o d service they h ave so faithfully delivered.
Their Chrom el elem ents are durable an d e a sy to get at. The furnaces sh o w n here are repre
sentative. H o sk in s M an u factu rin g C o m p an y, Detroit 8, M ich ig a n .
This F D -1 0 4 crucible furnace operates on the sam e principle a s the furnace above. Its heat
ing cham ber is 5 " diam eter x 5 " deep. . . . A ll our furnaces are described in C atalog 58.
Send for a copy.
lune, 1945 A N A L Y T I C A L E D I T I O N 15
SERVES ESSENTIAL CONTROL LABORATORIES
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B L U E L I N E
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C o n su lt L e a d in g L a b o ra to ry S u p p ly H o u s e s T h r o u g h o u t ! a n d C a n a d a fo r K im b le L ab orato ry
The V i s i b l e G ua ra n te e o f I n v i s i b l e Qu al ity
KIMBLE G L A S S C O M P A N Y • • • • V I N E L A N D , N. J.
N E W Y O R K • C H I C A G O • P H I L A D E L P H I A • D E T R O I T • 0 0 S T 0 N • I N D I A N A P O L I S • S A N F R A N C I S C O
16 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 17, No. 6
A . H .T . C O . S P E C I F I C A T I O N
G A S T R O T A R Y A I R P U M P S
Now available in two models, i.e. new Heavy Duty Model with capacity of 5.75 cu. ft. of free air per minute, and Portable Blast and Suction Apparatus with capacity of 1.3 cu. ft. per minute
GAST ROTARY AIR P U M P , Heavy D uty M odel, A.H.T. Co. Specification.
A quiet, fan-cooled, m otor driven un it, for continuous or in te rm itte n t use, cap
able of m oving 5.75 cu. ft. of free air per m inute. Delivers an y degree of vacuum up to 28 inches of m ercury or pressures up to 10 lbs. per square inch.
Consisting of pum p w ith slotted, eccentric ro to r w ith four sliding vanes, coupled to a ca
pacitor-type electric m otor, h.p., 1725 r.p.m ., w ith sleeve bearings and therm al overload circuit breaker, m ounted upon a m etal base on rubber feet. R o to r is fixed to J^-inch shaft fitted w ith ballbearings. W ith vacuum gauge, 0 to 30 inches of m ercury, and pressure gauge 0 to 50 lbs.; oil and air filters on inlet and o u tlet; pressure relief valve set a t approx. 20 lbs.;
and tw o bleeder petcocks for regulating vacuum and pressure.
T he combined filter, muffler an d tra p on th e pressure side is enclosed in cast iron; cartridge can be rem oved for clean
ing or replacem ent. T he combined oiling and air filtering device on th e vacuum side is enclosed in glass for observation of oil level.
Air Pump, Gast Rotary, Heavy Duty Model, as above described, complete w ith vacuum and pressure gauges, th erm al overload circuit breaker, filters, hose connectors for J4-inch tubing, an d 10 ft. cord w ith snap sw itch and plug. Power consum ption 460 w atts; n e t w eight 65 lbs. F or 115 volts, 60 cycles, single phase, a .c .. . 74.00 Ditto, b u t for 115 volts, d.c...85.00
“ “ “ 230 volts, 60 cycles, single phase, .a.c...74.00
1033-S.
1033-S.
1033-T.
1033-U.
GAST PORTABLE ROTARY AIR BLAST AND SUCTION APPARATUS, A.H.T. Co. Specifica
tion. A quiet, air cooled, m otor driven un it, com plete w ith vacuum and pressure gauges, and th erm al overload circuit breaker; suitable for continuous operation a t pressures not exceeding 20 lbs. or for in
te rm itte n t use up to 30 lbs.
C onsisting of pum p w ith four-vane ro to r which is integral w ith th e shaft of a K h.p. m otor. R o to r revolves in a precision m achined housing. W ith air filters an d oil tr a p directly behind inlet and o u tlet. V acuum
gauge reads 0 to 30 inches of m ercury, and pressure gauge 0 to 50 lbs. W ith safety valve adjusted a t 30 lbs., and bleeder petcocks for regulating pressure and vacuum as desired.
T h e com bined filter, muffle an d tr a p on pressure side is enclosed in cast iron; cartridge can be rem oved for cleaning or replacem ent.
T h e com bined oiling an d air filtering device on vacuum side is en
closed in glass for convenient observation of oil level.
Specifications: speed 1725 r.p .m .; m axim um pressure 20 to 30 lbs. per sq. in.; free air approx. 1.3 cu. ft. per m inute; operates four sm all blast lam ps;
m axim um vacuum 27 inches of m ercury; power consum ption 250 w atts; n e t w eight 32 lbs.
1 0 3 3 -G . G a st P o r ta b le R otary Air B la st an d S u c tio n A pp aratu s, A .H .T . Co. S p e cifica tio n , as a b o v e d escrib ed , c o m p le te w ith p ressure an d v a cu u m g a u g es, th erm a l o v erlo a d circu it b reaker, filters, ca rry in g h a n d le an d 10 ft . cord w ith sn a p s w itc h an d p lu g . For 110 v o lts , 60 cy c les, a .c ...3 3 .5 0 N O T E — A v a ila b le w ith m o to r fo r v o lta g e an d cu rren t sp e cifica tio n s o th er
th a n a b o v e a t s lig h tly h ig h er p rices.
M o r e d e t a i l e d i n f o r m a t io n s e n t u p o n r e q u e s t .
1033-G.
AR TH U R H. T H O M A S COMPANY
R E T A I L — W H O L E S A L E — E X P O R T
LABORATORY APPARATUS AND REAGENTS
W E S T W A S H I N G T O N S Q U A R E , P H I L A D E L P H I A 5, U .S.A.
Cable Address “ B alance,” Philadelphia
INDUSTRIAL a n d EN G IN EE R IN G CHEMISTRY
P U B L I S H E D B Y
T H E A M E R I C A N C H E M I C A L S O C I E T Y W A L T E R J. M U R P H Y ,
E D I T O R
Spectrographic A n a ly s is of M agn e siu m A ll o y s
B. L. A V E R B A C H 1 U. S. Radiator Corporation, Geneva, N . Y.
This study describes the spectrography of a magnesium-base alloy containing 6 % aluminum, 3 % zinc, and 0 . 2 0 % manganese. A statistical analysis of the procedure indicated that an accuracy of at least ± 5 % of the contained element was reasonable for this ma
terial. In addition, methods of casting a representative sample free from microshrinkage were investigated.
T
H E spectrographic process is capable of accurately analyzing constituents of fairly high percentage if sufficiently rigid conditions are imposed on th e process and on th e sam pling procedure. T his paper describes a procedure for th e rap id analy
sis of a magnesium -base alloy w ith a nom inal com position of 6 % alum inum , 3 % zinc, an d 0.20% manganese. D uring th e es
tab lish m en t of th is procedure a stu d y was m ade of th e repro
ducibility of th e process, an d of th e consistency of th e sam ple it
self. As experience w ith these analyses was gained it was real
ized th a t extrem ely close control was necessary to obtain con
sistent results.
T h e spectrographic equipm ent consisted of a spark generator of th e ro ta ry spark type, a high-voltage a ltern atin g cu rren t arc source, a large grating spectrograph, darkroom equipm ent for th e rap id processing of 35-mm. film, an d a photoelectric com- p arator-densitom eter to m easure th e location an d density of the spectral lines. All th is equipm ent was m an u factu red by the A pplied R esearch L aboratories an d th e H arry W. D ie te rt Com
pany.
A flat sand-cast disk was used on a P etrey spark stan d . D if
feren t types of specimens were found to be subject to extrem e variations in th e zinc a n d alum inum contents, a n d for th is reason m ethods of casting a suitable spectrograph specimen were also investigated.
E Q U I P M E N T
T he spectrograph was a sta n d a rd A R L -D ietert grating in s tru m en t w ith a dispersion of approxim ately 7 A. per m m . in th e first order. T hirty-five m illim eter E astm an Spectrum Analysis I film was used an d was processed in the following m anner:
1. T hree m inutes in D -19 developer a t 70° F.
2. F ive seconds in acetic acid short stop 3. T hree m inutes in E astm an liquid x-ray fixer 4. Five m inutes in running w ater
5. Rinse in distilled w ater 6. W ipe w ith cellulose sponge 7. One m in u te in infrared dryer
F o r excitation, th e sp ark u n it w as used alm ost exclusively.
Some effects of varying th e secondary inductance are described below, b u t all w ork was done w ith th e inductance a t its lowest possible value, approxim ately 0.045 mh. T here are indications th a t even lower inductances m ay be desirable.
T he com parator-densitom eter was of th e type which employs a m otor-driven scanning slit 12 m icrons wide an d 1.1 mm. long.
T his in stru m en t was set so th a t th e transm ission reading on
clear film w as 100. A t a density of 1.0, therefore, the transm is
sion reading was 10, an d a t a density of 2.0 th e reading was 1.0.
F o r accurate results, th e transm ission readings were confined betw een 80 an d 15, so th a t densities greater th a n 1.0 could n o t be used. N o background corrections were m ade.
W O R K I N G C U R V E S
T he p rep aratio n of emulsion calibration an d w orking curves has been adequately described (3, 4). F o r th e em ulsion calibra
tion, a ground quartz diffusing plate 1 mm . th ick was placed in fro n t of the spark to give b e tte r uniform ity along th e length of the line, b u t th is plate was n o t used during the actu a l analyses.
T he stan d ard s which were m ost suitable for th is application were the flat slabs supplied by th e A lum inum C om pany of America. In several instances th e stan d ard s of th e Dow Chemi
cal C om pany were also used. These stan d ard s were in approxi
m ately the sam e m etallurgical condition as the sam ples an d were handled in th e sam e fashion. T he range of chemical compositions of the various constituents in the stan d ard s covered ranges which were sim ilar to th e range in th e samples, so th a t errors due to th e effects of one elem ent on the emission characteristics of a n o th er were minim ized. F req u en t w et chemical checks were also m ade.
B oth stan d ard s an d sam ples were sparked under th e following conditions:
P o w er P rim a ry v o lta g e C a p a c ita n ce I n d u cta n ce P respark E x p o su re tim e S lit
4 / 3 k v a . 70 v o lts 0 .0 1 4 m fd.
0 .0 4 5 m h.
10 sec o n d s 2 5 t o 3 5 seco n d s 6 0 m icron s X 2 .6 m m .
1 P r e s e n t a d d ress, W o rk s L a b o ra to ry , G en eral E le c tr ic C o ., S c h e n e c ta d y , N . Y .
I n th e p rep aratio n of all magnesium sam ples an d stan d ard s th e sam e procedure w as used. A 0.16-cm. (0.06-inch) c u t was tak en from one surface w ith a lathe, a n d th is surface was sanded w ith a N o. 120 Aloxite belt. T his surface was used against a spectrographically pure carbon rod in the P etrey stand, an d th e conditions m entioned above were m aintained.
I n th e choice of th e analysis lines several conditions m ust be considered:
. 1 . T here should be no interfering lines of o th er elem ents pres
en t. F o r best results th e background should also be low.
2. T his line should have a suitable density for th e concen
tra tio n range in w hich i t is used. F o r m axim um accuracy the ratio of th e densities of the analysis line an d th e reference line should be near unity.
3. If possible, th e reference an d analysis lines should be a homologous pair—th a t is, th ey should react sim ilarly to slight changes in excitation conditions. T he s ta te of ionization is a valuable guide, b u t n o t alw ays a com pletely reliable criterion of a homologous pair. A fter a set of lines has been used for some tim e, this condition m ay be determ ined from experience.
4. T he sta n d a rd an d th e analysis lines should be as close to each o th er as possible because of the change in th e film gam m a w ith wave length.
I n practice it was virtually impossible to obtain all these con
ditions for every line. Since it was desirable to m ake th e entire analysis a t one exposure, th e lines were split horizontally w ith a 341
342 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 17, No. 6 ro tatin g sector a t th e secondary focus. T he top half was ex
posed to four tim es as m uch light as th e bottom half. W ith this arrangem ent alum inum , zinc, magnesium , and m anganese lines were read on th e bottom half, while iron, silicon, copper, and nickel were read on th e upper half.
' F o r each exposure th e following lines were read:
W a v e L en g th ,
À. M g R eferen c e R em ark s
A1 35 8 7 3 3 3 0 N o t h o m o lo g o u s
Zn 3302 33 3 0 H o m o lo g o u s
M n 26 1 0 3 0 7 4 H o m o lo g o u s
Si 25 1 6 3 0 7 4 H o m o lo g o u s
F e 2382 30 7 4 N o t h o m o lo g o u s
C u 32 7 4 3 0 7 4 H o m o lo g o u s
U nfortunately nickel could n o t be determ ined in this exposure, and a separate determ ination under th e following conditions was taken:
P o w er Prespark E x p o su re In d u cta n ce
4 / 3 k v a . 10 seco n d s 5 0 seco n d s 0 .3 6 5 m h.
atm osphere should be m aintained. Changes in exposure time were necessary to follow th e changes in th e seasons. A daily record was k ep t of th e hum idity, and it was evident th a t as the relative hum idity increased, th e exposure tim e increased.
An ultraviolet lam p was tried a t the ro tatin g spark gap. Pre
vious reports had indicated th a t irradiation of th e rotating spark gap should reduce th e errors due to variations in excitation.
The lam p which was installed was one of very sm all o u tp u t sup
plied by th e m anufacturer. N o difference in reproducibility was discernible w ith th e lam p in or out, and th e consistency stu d ies shown later were m ade w ithout the lam p. W ith th e rotary gap irradiated, exposures h ad to be increased by about 5 seconds.
These lim ited experiments by no m eans exclude the possibilities of im proving th e reproducibility by irradiating the ro tatin g spark gap, since the original experim ents were m ade w ith a much more powerful ultraviolet lam p (about 250 w atts).
In addition to these uncontrollable variables, there was a set of variables which could be controlled. T he 4 /3 kva. power tap was chosen to give readable line densities w ith a reasonable ex
posure time. A t th e rotating spark gap a voltage of 80 volts was first used. L ater trials, however, indicated th a t 70 volts
T he additional exposure and inductance seemed to sensitize , N i 3415 . , , , . , , the nickel line, so th a t the „ „ pair was suitable for nickel
Mg 3074
contents as low as 0.001%. None of th e samples contained a de
tectable am ount of nickel, b u t since th e specifications allow only 0.01% nickel, it was necessary to check each h e a t for its presence.
In some instances plain glass filters m ade from microscope cover glasses were tried directly in front of th e film to reduce th e intensity of a particu lar line. These filters were very satisfactory, since th ey allowed th e exposure condition to be adjusted so th a t the ratios of th e densities of th e analysis and reference lines were close to unity. T he filter did n o t affect th e shape or slope of the working curves, b u t for the above procedure no filters were used.
Figure 1 shows some of th e working curves for alum inum , zinc, an d manganese. Sim ilar curves were used for silicon, copper, iron, an d nickel.
T he usability of these curves is dependent to a large extent on th e slope. If th e curve is too steep it is impossible to deter
mine the elem ent concentration w ith any degree of accuracy, and if i t is excessively shallow it is difficult to cover th e permissible range w ith one curve. T he accuracy of the alum inum deter
m ination, shown in Figure 1, is p articularly sensitive to th e slope because of th e large percentage of contained alum inum . A t 3587 A. the line is broad and diffuse and is actually composed of a num ber of lines. Experience showed, however, th a t it followed th e alum inum content faithfully and seemed to have th e shallow
est slope of the available alum inum lines.
Theoretically these curves should be good indefinitely, b u t they m u st be frequently checked against standards. F o r small variations from th e curve, small corrections m ay be m ade, b u t if th e correction is greater th a n 5% of th e contained elem ent, the entire curve should be redeterm ined. T he exact causes for some of these shifts have not been satisfactorily explained. I t is very seldom th a t the entire set of elem ents will shift a t th e sam e time.
In th is p articular system zinc and alum inum seemed to be the w orst offenders, b u t even th en th ey seldom shifted together.
I t is well know n th a t th e prim ary in p u t voltage should be carefully controlled for th e m axim um accuracy. F or the best results a large m otor generator set should be used. U nfortu
nately th e 225-volt in p u t to this installation came directly from th e line, an d this m ay have been a contributing factor to th e curve shifting. W hen, however, the in p u t voltage was deliberately varied from 200 to 240 it was impossible to reproduce these shifts consistently.
Changes in hum idity are often blam ed for these variations, and for th e best results a constant-tem perature, constant-hum idity
BATIO Z n 330 2 Mg 3330
RATIO AI 358 7 Mg 3 3 3 0
Figure 1. Working Curves for Aluminum, Manganese, and Zinc
June, 1945 A N A L Y T I C A L E D I T I O N 343
Table I. Effect of Inductance on Line Densities and Intensity Ratios L in e _________________T ra n sm issio n R ea d in g s__________________
I n d u c ta n c e , M illih e n r y s
0 .0 4 5 0 . 0 9 0 0 . 1 8 0 0 .3 6 5 0 . 7 3 0 1 .0 9 5 1 .4 6
Fe 23 8 2 T 6 6 . 0 6 7 . 0 5 8 .5 7 3 . 0 9 2 . 5
R 0 . 7 4 0 .6 1 0 . 5 5 0 . 3 9 0 . 3 5
S i 25 1 6 T 7 8 .0 7 2 . 0 4 8 . 0 3 9 . 0 6 4 .5 s s . o
R 0 . 5 8 0 .5 6 0 . 6 5 0 . 6 8 0 .7 3 0 .7 3
M n 2 6 1 0 T 8 0 .0 7 9 . 0 7 7 . 0 8 6 .0 9 6 . 0 R 0 . 5 5 0 . 4 8 0 . 4 0 0 . 2 9 0 . 2 6
M g 3 0 7 4 T 4 6 . 0 3 6 . 0 2 2 . 5 1 9 .0 4 4 .0 7 7 . 0 9 2 . 0 C u 3 2 7 4 T 5 8 . 0 5 5 . 0 2 9 . 0 2 2 .0 3 5 . 0 6 4 .0 7 8 . 0
R 0 .8 3 0 . 7 5 0 . 8 8 0 . 9 5 1 .1 5 1 .2 9 1 .6 1
Zn 3 3 0 2 T 2 4 .5 1 1 .0 3 . 5 1 .2 2 . 8 6 . 9 1 8 .0
R 1 .3 9 1 .6 9 1 .6 0 1 .4 4 1 .5 1 1 .5 2 1 .5 7
M g 3 3 3 0 T 4 4 . 0 3 2 . 0 1 0 .0 2 . 9 7 . 0 1 9 .5 4 1 .0
Al 3 5 8 7 T 1 6 .5 4 6 . 0 7 0 . 0 9 0 . 0
R 1 .6 8 0 . 7 7 0 .3 1 0 . 0 8
T . A v e ra g e o f th r e e tra n sm issio n rea d in g s.
R . I n t e n s it y ra tio , Z n, A1 w ith 3 3 3 0 ; o th er s w ith 3 0 7 4 . P o w e r 4 / 3 k va.
L ine v o lta g e 2 3 5 v o lt s ; in p u t v o lt a g e 7 0 v o lt s . A p e rtu re 2 , S e c to r 4 to 1, s lit 6 0 m ic ro n s, presp ark 10 s e c o n d s, ex p o su r e 5 0 s e c o n d s. I n d u c ta n c e w as th e o n ly th in g c h a n g e d d u rin g th e e x p er im en t.
provided m ore uniform results, p a rtly because th e lower voltage could be m aintained a t a m ore constant level.
T he spacing betw een th e tungsten points of th e ro to r an d th e s ta to r of th e ro ta tin g gap was very critical. A spacing of 0.25 mm . (0.010 inch) was m aintained, an d th e points were turned and spaced frequently to ensure their accurate alignm ent.
F or the best results this ad ju stm en t should be m ade after a num ber of exposures, so th a t th e entire system is som ew hat near its operating tem perature. S tartin g from cold, th e sam e tim e of exposure produced stronger an d stronger lines u n til the operating tem perature was reached. Bringing th e points too close together reduced th e voltage m arkedly, and if the back and front gaps were n o t equally spaced erratic results were produced.
Too m uch emphasis cannot be placed on m aintaining th e proper spacing a t the ro ta ry gap.
clip holding th e carbon rod against th e stage. If this was not done, discharges were a p t to occur a t o th er places in th e circuit.
A ttem pts to use th e high-voltage alternating current arc showed th a t this m ethod was n o t so consistent as th e spark process for th e high percentage elem ents. F o r m inor constitu
ents such as iron, copper, silicon, and nickel it was suitable, b u t there was a saving in tim e b y m aking th e complete analysis a t one exposure w ith th e spark unit.
C hanging th e secondary inductance h ad a selective effect on th e density of th e individual lines. T able I shows th e transm is
sion readings for a series of exposures in which only th e inductance was changed. As th e inductance increased, the density of th e iron line first increased slightly and th en becam e very weak.
T he intensity ratio, however, showed a steady decrease. T he silicon line also w ent through a m axim um density b u t th e ratios showed a steady increase as th e inductance increased. M anga
nese showed only a slight effect, b u t as th e inductance increased it tended to disappear.
M agnesium 3074 and 3330 bo th w ent through a m axim um in
tensity a t 0.365 m h. Copper and zinc also passed through a m axim um intensity a t th e sam e value of inductance. Alumi
num , however, tended to become extrem ely light as th e induc
tance increased, and eventually th e line disappeared.
A suitable system can probably be worked o u t for any of these inductance values, b u t all other work in this report was perform ed a t th e lowest possible inductance. In fact, th e above d a ta sug
gest th a t even lower inductances should be tried.
P R O C E S S R E P R O D U C I B IL IT Y
To check the reproducibility of th e process a ru n of 108 de
term inations was m ade on a stan d ard disk of th e following com
position:
%
A l 5 .8 3
Zn 3 .2 1
M n 0 .2 1
M g B a la n ce
STANDARD SM
MODI STAf DEVI COEVARI
DARD ATlON: 0 0 5 8 T ICIEN T OF ATION - 0 5 6
1.19
= 119
— = 4 4 6 % R EA D IN 6S
0 9 8 1.04 1.10 U6 122 RATIO 3 5 8 7 Al
3 3 3 0 Mg
Figure 2. Frequency Distribution Chart for Aluminum
To prev en t sparking between th e specimen an d the stage it was necessary to keep th e stage clean w ith fine em ery p ap er an d to place a w eight on th e disk while it was being sparked. I t was also necessary to keep th e stage clean a t th e points where it con
ta c te d th e carbon rod, and to keep a high pressure on the spring
Ail determ inations were m ade on th e sam e day w ith all ele
m ents of th e process carefully controlled. Frequency-dispersion curves were draw n using th e sta n d a rd term inology of th e A.S.- T .M . (1). F o r convenience, a brief description of th e term s used is given.
X = arith m etic average
Mode = value w hich occurs m ost frequently
a — sta n d a rd deviation = the square root of th e average of th e squares of th e deviations of a set of N num ber from th eir average, X
V = coefficient of v ariatio n = ratio of the sta n d a rd de
v iation to th e average = 100 a / X N = num ber of determ inations
Figure 2 shows th e frequency dispersion characteristics of the alum inum determ ination expressed as a function of th e intensity ratios.
F or alum inum : a = 0.058 in ten sity un it V = 4.92%
If these deviations are expressed as percentages of alum inum :
<r = 0.26% Al
V = 4.46% of th e alum inum present
T o aid in th e in terp re tatio n of these results th e following ad d i
tional statem en ts m ay be m ade:
/ i \
of th e to ta l num - If X , a-, andiV are stated , more th a n ^1 —
ber N observations lie w ithin th e closed range, X =t ter. T his is tru e even if th e results are obtained under uncontrolled condi
tions. S ta te d an o th er way, a t least 75% of th e results m ust lie w ithin ± 2a.
